System and method for operating a packaged terminal air conditioner unit

ABSTRACT

A packaged terminal air conditioner unit (PTAC) and methods for operating the same are provided. A PTAC controller is operably coupled to a compressor and an indoor fan for performing a cooling cycle. The compressor is stopped after the indoor temperature drops below a target temperature, but the indoor fan continues to circulate air through an indoor portion of the PTAC until a fan stop condition occurs. The fan stop condition occurs when the discharge temperature is at or above the dew point temperature to prevent condensation on components within the indoor portion of the PTAC.

FIELD OF THE INVENTION

The present disclosure relates generally to air conditioner units, and more particularly to methods of reducing condensate production within packaged terminal air conditioner units.

BACKGROUND OF THE INVENTION

Air conditioner or conditioning units are conventionally utilized to adjust the temperature indoors—i.e. within structures such as dwellings and office buildings. Such units commonly include a closed refrigeration loop to heat or cool the indoor air. Typically, the indoor air is recirculated while being heated or cooled. A variety of sizes and configurations are available for such air conditioner units. For example, some units may have one portion installed within the indoors that is connected, by e.g., tubing carrying the refrigerant, to another portion located outdoors. These types of units are typically used for conditioning the air in larger spaces.

Another type of unit, sometimes referred to as a packaged terminal air conditioner unit (PTAC), may be used for somewhat smaller indoor spaces that are to be air conditioned. These units may include both an indoor portion and an outdoor portion separated by a bulkhead and may be installed in windows or positioned within an opening of an exterior wall of a building. When a conventional PTAC is operating in a cooling mode, the local surfaces around the discharge vent on the indoor side can become colder than the bulk dew point of the room that is being conditioned. After a cooling operation has dropped the room temperature below the target set point, a typical PTAC may turn off loads including the compressor, the indoor fan, and the outdoor fan. However, the local surfaces near the discharge vent may then experience some condensation due to moist ambient air contacting these cooler surfaces.

Accordingly, improved air conditioner units and methods for reducing condensation within these units would be useful. More specifically, a packaged terminal air conditioner unit that regulates the temperatures of components proximate the discharge vent would be particularly beneficial.

BRIEF DESCRIPTION OF THE INVENTION

The present subject matter provides a packaged terminal air conditioner unit (PTAC) and methods for operating the same. A PTAC controller is operably coupled to a compressor and an indoor fan for performing a cooling cycle. The compressor is stopped after the indoor temperature drops below a target temperature, but the indoor fan continues to circulate air through an indoor portion of the PTAC until a fan stop condition occurs. The fan stop condition occurs when the discharge temperature is at or above the dew point temperature to prevent condensation on components within the indoor portion of the PTAC. Additional aspects and advantages of the invention will be set forth in part in the following description, may be obvious from the description, or may be learned through practice of the invention.

In accordance with one embodiment, a packaged terminal air conditioner is provided. The packaged terminal air conditioner unit includes a bulkhead defining an indoor portion and an outdoor portion and a refrigeration loop including an outdoor heat exchanger positioned within the outdoor portion and an indoor heat exchanger positioned within the indoor portion. A compressor is operably coupled to the refrigeration loop and is configured for urging a flow of refrigerant through the outdoor heat exchanger and the indoor heat exchanger and an indoor fan is configured for urging a flow of discharge air through the indoor heat exchanger and out a discharge vent. A controller is operably coupled to the compressor and the indoor fan and is configured for operating the compressor and the indoor fan to lower an indoor temperature, determining that the indoor temperature has dropped to a target room temperature, stopping the compressor in response to determining that the indoor temperature has dropped to the target room temperature, operating the indoor fan after stopping the compressor, and stopping the indoor fan when a fan stop condition occurs.

In accordance with another embodiment, a method of operating a packaged terminal air conditioner unit is provided. The packaged terminal air conditioner unit includes a compressor and an indoor fan. The method includes operating the compressor and the indoor fan to lower an indoor temperature, determining that the indoor temperature has dropped to a target room temperature, stopping the compressor in response to determining that the indoor temperature has dropped to the target room temperature, operating the indoor fan after stopping the compressor, and stopping the indoor fan when a fan stop condition occurs.

According to still another embodiment, an air conditioner unit is provided including a compressor configured for urging a flow of refrigerant through an outdoor heat exchanger and an indoor heat exchanger and an indoor fan configured for urging a flow of discharge air through the indoor heat exchanger and out a discharge vent. A controller is operably coupled to the compressor, the indoor fan, a discharge temperature sensor, and a humidity sensor, the controller being configured for operating the compressor and the indoor fan to lower an indoor temperature, stopping the compressor when the indoor temperature drops below a target temperature, obtaining a dew point temperature using the humidity sensor, determining a fan stop temperature based on the dew point temperature, obtaining a discharge temperature using the discharge temperature sensor, and stopping the indoor fan when the discharge temperature exceeds the fan stop temperature.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of an air conditioner unit, with part of an indoor portion exploded from a remainder of the air conditioner unit for illustrative purposes, in accordance with one exemplary embodiment of the present disclosure.

FIG. 2 is another perspective view of components of the indoor portion of the exemplary air conditioner unit of FIG. 1.

FIG. 3 is a schematic view of a refrigeration loop in accordance with one embodiment of the present disclosure.

FIG. 4 is a rear perspective view of an outdoor portion of the exemplary air conditioner unit of FIG. 1, illustrating a vent aperture in a bulkhead in accordance with one embodiment of the present disclosure.

FIG. 5 is a front perspective view of the exemplary bulkhead of FIG. 4 with a vent door illustrated in the open position in accordance with one embodiment of the present disclosure.

FIG. 6 is a rear perspective view of the exemplary air conditioner unit and bulkhead of FIG. 4 including a fan assembly for providing make-up air in accordance with one embodiment of the present disclosure.

FIG. 7 is a side cross sectional view of the exemplary air conditioner unit of FIG. 1.

FIG. 8 depicts certain components of a controller according to example embodiments of the present subject matter.

FIG. 9 illustrates a method for controlling a packaged terminal air conditioner unit in accordance with one embodiment of the present disclosure.

FIG. 10 illustrates a plot of a dew point temperature and a discharge temperature after a compressor has been turned off according to an exemplary embodiment of the present subject matter.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Referring now to FIGS. 1 and 2, an air conditioner unit 10 is provided. The air conditioner unit 10 is a one-unit type air conditioner, also conventionally referred to as a room air conditioner or a packaged terminal air conditioner (PTAC). The unit 10 includes an indoor portion 12 and an outdoor portion 14, and generally defines a vertical direction V, a lateral direction L, and a transverse direction T. Each direction V, L, T is perpendicular to each other, such that an orthogonal coordinate system is generally defined.

A housing 20 of the unit 10 may contain various other components of the unit 10. Housing 20 may include, for example, a rear grill 22 and a room front 24 which may be spaced apart along the transverse direction T by a wall sleeve 26. The rear grill 22 may be part of the outdoor portion 14, and the room front 24 may be part of the indoor portion 12. Components of the outdoor portion 14, such as an outdoor heat exchanger 30, an outdoor fan 32, and a compressor 34 may be housed within the wall sleeve 26. A fan shroud 36 may additionally enclose outdoor fan 32, as shown.

Indoor portion 12 may include, for example, an indoor heat exchanger 40, a blower fan or indoor fan 42, and a heating unit 44. These components may, for example, be housed behind the room front 24. Additionally, a bulkhead 46 may generally support and/or house various other components or portions thereof of the indoor portion 12, such as indoor fan 42 and the heating unit 44. Bulkhead 46 may generally separate and define the indoor portion 12 and outdoor portion 14.

Outdoor and indoor heat exchangers 30, 40 may be components of a refrigeration loop 48, which is shown schematically in FIG. 3. Refrigeration loop 48 may, for example, further include compressor 34 and an expansion device 50. As illustrated, compressor 34 and expansion device 50 may be in fluid communication with outdoor heat exchanger 30 and indoor heat exchanger 40 to flow refrigerant therethrough as is generally understood. More particularly, refrigeration loop 48 may include various lines for flowing refrigerant between the various components of refrigeration loop 48, thus providing the fluid communication there between. Refrigerant may thus flow through such lines from indoor heat exchanger 40 to compressor 34, from compressor 34 to outdoor heat exchanger 30, from outdoor heat exchanger 30 to expansion device 50, and from expansion device 50 to indoor heat exchanger 40. The refrigerant may generally undergo phase changes associated with a refrigeration cycle as it flows to and through these various components, as is generally understood. Suitable refrigerants for use in refrigeration loop 48 may include pentafluoroethane, difluoromethane, or a mixture such as R410a, although it should be understood that the present disclosure is not limited to such example and rather that any suitable refrigerant may be utilized.

As is understood in the art, refrigeration loop 48 may be alternately be operated as a refrigeration assembly (and thus perform a refrigeration cycle) or a heat pump (and thus perform a heat pump cycle). As shown in FIG. 3, when refrigeration loop 48 is operating in a cooling mode and thus performs a refrigeration cycle, the indoor heat exchanger 40 acts as an evaporator and the outdoor heat exchanger 30 acts as a condenser. Alternatively, when the assembly is operating in a heating mode and thus performs a heat pump cycle, the indoor heat exchanger 40 acts as a condenser and the outdoor heat exchanger 30 acts as an evaporator. The outdoor and indoor heat exchangers 30, 40 may each include coils through which a refrigerant may flow for heat exchange purposes, as is generally understood.

According to an example embodiment, compressor 34 may be a variable speed compressor. In this regard, compressor 34 may be operated at various speeds depending on the current air conditioning needs of the room and the demand from refrigeration loop 48. For example, according to an exemplary embodiment, compressor 34 may be configured to operate at any speed between a minimum speed, e.g., 1500 revolutions per minute (RPM), to a maximum rated speed, e.g., 3500 RPM. Notably, use of variable speed compressor 34 enables efficient operation of refrigeration loop 48 (and thus air conditioner unit 10), minimizes unnecessary noise when compressor 34 does not need to operate at full speed, and ensures a comfortable environment within the room.

In exemplary embodiments as illustrated, expansion device 50 may be disposed in the outdoor portion 14 between the indoor heat exchanger 40 and the outdoor heat exchanger 30. According to the exemplary embodiment, expansion device 50 may be an electronic expansion valve that enables controlled expansion of refrigerant, as is known in the art. More specifically, electronic expansion device 50 may be configured to precisely control the expansion of the refrigerant to maintain, for example, a desired temperature differential of the refrigerant across the indoor heat exchanger 40. In other words, electronic expansion device 50 throttles the flow of refrigerant based on the reaction of the temperature differential across indoor heat exchanger 40 or the amount of superheat temperature differential, thereby ensuring that the refrigerant is in the gaseous state entering compressor 34. According to alternative embodiments, expansion device 50 may be a capillary tube or another suitable expansion device configured for use in a thermodynamic cycle.

According to the illustrated exemplary embodiment, outdoor fan 32 is an axial fan and indoor fan 42 is a centrifugal fan. However, it should be appreciated that according to alternative embodiments, outdoor fan 32 and indoor fan 42 may be any suitable fan type. In addition, according to an exemplary embodiment, outdoor fan 32 and indoor fan 42 are variable speed fans. For example, outdoor fan 32 and indoor fan 42 may rotate at different rotational speeds, thereby generating different air flow rates. It may be desirable to operate fans 32, 42 at less than their maximum rated speed to ensure safe and proper operation of refrigeration loop 48 at less than its maximum rated speed, e.g., to reduce noise when full speed operation is not needed. In addition, according to alternative embodiments, fans 32, 42 may be operated to urge make-up air into the room.

According to the illustrated embodiment, indoor fan 42 may operate as an evaporator fan in refrigeration loop 48 to encourage the flow of air through indoor heat exchanger 40. Accordingly, indoor fan 42 may be positioned downstream of indoor heat exchanger 40 along the flow direction of indoor air and downstream of heating unit 44. Alternatively, indoor fan 42 may be positioned upstream of indoor heat exchanger 40 along the flow direction of indoor air, and may operate to push air through indoor heat exchanger 40.

Heating unit 44 in exemplary embodiments includes one or more heater banks 60. Each heater bank 60 may be operated as desired to produce heat. In some embodiments as shown, three heater banks 60 may be utilized. Alternatively, however, any suitable number of heater banks 60 may be utilized. Each heater bank 60 may further include at least one heater coil or coil pass 62, such as in exemplary embodiments two heater coils or coil passes 62. Alternatively, other suitable heating elements may be utilized.

The operation of air conditioner unit 10 including compressor 34 (and thus refrigeration loop 48 generally) indoor fan 42, outdoor fan 32, heating unit 44, expansion device 50, and other components of refrigeration loop 48 may be controlled by a processing device such as a controller 64. Controller 64 may be in communication (via for example a suitable wired or wireless connection) to such components of the air conditioner unit 10. As described in more detail below with respect to FIG. 8, controller 64 may include a memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of unit 10. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor.

Unit 10 may additionally include a control panel 66 and one or more user inputs 68, which may be included in control panel 66. The user inputs 68 may be in communication with the controller 64. A user of the unit 10 may interact with the user inputs 68 to operate the unit 10, and user commands may be transmitted between the user inputs 68 and controller 64 to facilitate operation of the unit 10 based on such user commands. A display 70 may additionally be provided in the control panel 66, and may be in communication with the controller 64. Display 70 may, for example be a touchscreen or other text-readable display screen, or alternatively may simply be a light that can be activated and deactivated as required to provide an indication of, for example, an event or setting for the unit 10.

Referring briefly to FIG. 4, a vent aperture 80 may be defined in bulkhead 46 providing fluid communication between indoor portion 12 and outdoor portion 14. Vent aperture 80 may be utilized in an installed air conditioner unit 10 to allow outdoor air to flow into the room through the indoor portion 12. In this regard, in some cases it may be desirable to allow outside air (i.e., “make-up air”) to flow into the room in order, e.g., to meet government regulations, to compensate for negative pressure created within the room, etc. In this manner, according to an exemplary embodiment, make-up air may be provided into the room through vent aperture 80 when desired.

As shown in FIG. 5, a vent door 82 may be pivotally mounted to the bulkhead 46 proximate to vent aperture 80 to open and close vent aperture 80. More specifically, as illustrated, vent door 82 is pivotally mounted to the indoor facing surface of indoor portion 12. Vent door 82 may be configured to pivot between a first, closed position where vent door 82 prevents air from flowing between outdoor portion 14 and indoor portion 12, and a second, open position where vent door 82 is in an open position (as shown in FIG. 5) and allows make-up air to flow into the room. According to the illustrated embodiment vent door 82 may be pivoted between the open and closed position by an electric motor 84 controlled by controller 64, or by any other suitable method.

In some cases, it may be desirable to treat or condition make-up air flowing through vent aperture 80 prior to blowing it into the room. For example, outdoor air which has a relatively high humidity level may require treating before passing into the room. In addition, if the outdoor air is cool, it may be desirable to heat the air before blowing it into the room. Therefore, according to an exemplary embodiment of the present subject matter, unit 10 may further include an auxiliary sealed system that is positioned over vent aperture 80 for conditioning make-up air. The auxiliary sealed system may be a miniature sealed system that acts similar to refrigeration loop 48, but conditions only the air flowing through vent aperture 80. According to alternative embodiments, such as that described herein, make-up air may be urged through vent aperture 80 without the assistance of an auxiliary sealed system. Instead, make-up air is urged through vent aperture 80 may be conditioned at least in part by refrigeration loop 48, e.g., by passing through indoor heat exchanger 40. Additionally, the make-up air may be conditioned immediately upon entrance through vent aperture 80 or sequentially after combining with the air stream induced through indoor heat exchanger 40.

Referring now to FIG. 6, a fan assembly 100 will be described according to an exemplary embodiment of the present subject matter. According to the illustrated embodiment, fan assembly 100 is generally configured for urging the flow of makeup air through vent aperture 80 and into a conditioned room without the assistance of an auxiliary sealed system. However, it should be appreciated that fan assembly 100 could be used in conjunction with a make-up air module including an auxiliary sealed system for conditioning the flow of make-up air. As illustrated, fan assembly 100 includes an auxiliary fan 102 for urging a flow of make-up air through a fan duct 104 and into indoor portion 12 through vent aperture 80.

According to the illustrated embodiment, auxiliary fan 102 is an axial fan positioned at an inlet of fan duct 104, e.g., upstream from vent aperture 80. However, it should be appreciated that any other suitable number, type, and configuration of fan or blower could be used to urge a flow of makeup air according to alternative embodiments. In addition, auxiliary fan 102 may be positioned in any other suitable location within air conditioner unit 10 and auxiliary fan 102 may be positioned at any other suitable location within or in fluid communication with fan duct 104. The embodiments described herein are only exemplary and are not intended to limit the scope present subject matter.

Referring now to FIG. 7, operation of unit 10 will be described according to an exemplary embodiment. More specifically, the operation of components within indoor portion 12 will be described during a cooling operation or cooling cycle of unit 10. To simplify discussion, the operation of auxiliary fan 102 for providing make-up air through vent aperture 80 will be omitted, e.g., as if vent door 82 were closed. Although a cooling cycle will be described, it should be further appreciated that indoor heat exchanger 40 and/or heating unit 44 be used to heat indoor air according to alternative embodiments. Moreover, although operation of unit 10 is described below for the exemplary packaged terminal air conditioner unit, it should be further appreciated that aspects the present subject matter may be used in any other suitable air conditioner unit, such as a heat pump or split unit system.

As illustrated, room front 24 of unit 10 generally defines an intake vent 110 and a discharge vent 112 for use in circulating a flow of air (indicated by arrows 114) throughout a room. In this regard, indoor fan 42 is generally configured for drawing in air 114 through intake vent 110 and urging the flow of air through indoor heat exchanger 40 before discharging the air 114 out of discharge vent 112. According to the illustrated embodiment, intake vent 110 is positioned proximate a bottom of unit 10 and discharge vent 112 is positioned proximate a top of unit 10. However, it should be appreciated that according to alternative embodiments, intake vent 110 and discharge vent 112 may have any other suitable size, shape, position, or configuration.

During a cooling cycle, refrigeration loop 48 is generally configured for urging cold refrigerant through indoor heat exchanger 40 in order to lower the temperature of the flow of air 114 before discharging it back into the room. Specifically, during a cooling operation, controller 64 may be provided with a target temperature, e.g., as set by a user for the desired room temperature. In general, components of refrigeration loop 48, outdoor fan 32, indoor fan 42, and other components of unit 10 operate to continuously cool the flow of air. Notably, when a cooling cycle ends, various components within indoor portion 12 may be very cold such that condensate may have a tendency to form on such components. The formation of such condensation can cause serious problems, such as the formation of mold, mildew, or rust on components of unit 10. As described in more detail below, methods of operating unit 10 will be described which may prevent these problems and to raise the temperature of components of unit 10 after a cooling cycle.

In order to facilitate operation of refrigeration loop 48 and other components of unit 10, unit 10 may include a variety of sensors for detecting conditions internal and external to the unit 10. These conditions can be fed to controller 64 which may make decisions regarding operation of unit 10 to rectify undesirable conditions or to otherwise condition the flow of air 114 into the room. For example, as best illustrated in FIG. 7, unit 10 may include an indoor temperature sensor 120 which is positioned and configured for measuring the indoor temperature within the room. In this manner, unit 10 may be used to regulate the flow of air 114 into the room until the measured indoor temperature reaches the desired target temperature.

In addition, unit 10 includes the discharge temperature sensor 122 that is positioned within indoor portion 12 and is generally configured for measuring a discharge temperature. As used herein, “discharge temperature” is used generally to refer to the temperature of the flow of air 114 as it exits discharge vent 112. Thus, in order to obtain the most accurate measurement, discharge temperature sensor 122 may be positioned directly on or proximate to discharge vent 112, e.g., such that it is downstream of indoor fan 42 and indoor heat exchanger 40. Notably, measuring the temperature of the flow of discharge air 114 at this location may provide a good indication of the temperature of components within indoor portion 12. In this regard, some of the lowest temperatures may typically be experienced at discharge vent 112 because it is downstream of indoor heat exchanger 40. Therefore, when trying to determine where condensation is most likely to occur, detecting the temperature at this location is most instructive.

Referring still to FIG. 7, unit 10 may further include a humidity sensor 124 is positioned within indoor portion 12 and being configured for measuring an indoor humidity or relative humidity. According to the illustrated embodiment, the humidity sensor 124 is positioned upstream of indoor fan 42, e.g., between indoor heat exchanger 40 and indoor fan 42. According to the exemplary methods described below, humidity sensor 124 may be used for measuring humidity which may be used by controller 64 to determine a dew point temperature of the flow of air 114 using calculations known in the art. In this regard, the dew point temperature is the temperature to which the flow of air 114 must be cooled to become saturated with water vapor, such that condensation will occur on components of unit 10.

FIG. 8 depicts certain components of controller 64 according to example embodiments of the present disclosure. Controller 64 can include one or more computing device(s) 130 which may be used to implement methods as described herein. Computing device(s) 130 can include one or more processor(s) 130A and one or more memory device(s) 130B. The one or more processor(s) 130A can include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field-programmable gate array (FPGA), logic device, one or more central processing units (CPUs), graphics processing units (GPUs) (e.g., dedicated to efficiently rendering images), processing units performing other specialized calculations, etc. The memory device(s) 130B can include one or more non-transitory computer-readable storage medium(s), such as RAM, ROM, EEPROM, EPROM, flash memory devices, magnetic disks, etc., and/or combinations thereof.

The memory device(s) 130B can include one or more computer-readable media and can store information accessible by the one or more processor(s) 130A, including instructions 130C that can be executed by the one or more processor(s) 130A. For instance, the memory device(s) 130B can store instructions 130C for running one or more software applications, displaying a user interface, receiving user input, processing user input, etc. In some implementations, the instructions 130C can be executed by the one or more processor(s) 130A to cause the one or more processor(s) 130A to perform operations, e.g., such as one or more portions of methods described herein. The instructions 130C can be software written in any suitable programming language or can be implemented in hardware. Additionally, and/or alternatively, the instructions 130C can be executed in logically and/or virtually separate threads on processor(s) 130A.

The one or more memory device(s) 130B can also store data 130D that can be retrieved, manipulated, created, or stored by the one or more processor(s) 130A. The data 130D can include, for instance, data to facilitate performance of methods described herein. The data 130D can be stored in one or more database(s). The one or more database(s) can be connected to controller 64 by a high bandwidth LAN or WAN, or can also be connected to controller through network(s) (not shown). The one or more database(s) can be split up so that they are located in multiple locales. In some implementations, the data 130D can be received from another device.

The computing device(s) 130 can also include a communication module or interface 130E used to communicate with one or more other component(s) of controller 64 or unit 10 over the network(s). The communication interface 130E can include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, or other suitable components.

Now that the construction of air conditioner unit 10 and the configuration of controller 64 according to exemplary embodiments have been presented, an exemplary method 200 of operating a packaged terminal air conditioner unit will be described. Although the discussion below refers to the exemplary method 200 of operating air conditioner unit 10, one skilled in the art will appreciate that the exemplary method 200 is applicable to the operation of a variety of other air conditioning appliances. In exemplary embodiments, the various method steps as disclosed herein may be performed by controller 64 or a separate, dedicated controller.

Referring now to FIG. 9, method 200 includes, at step 210, operating the compressor and indoor fan to lower an indoor temperature. In this regard, as described briefly above, during a cooling cycle, the compressor urges a flow of refrigerant through an indoor heat exchanger, an outdoor heat exchanger, and an expansion device such that indoor heat exchanger 40 is very cold relative to the indoor temperature and thus absorbs thermal energy from the indoor air. The compressor continues to circulate refrigerant and the indoor fan continues to urge the flow of air through the indoor heat exchanger until a target temperature of the room is reached. Thus, step 220 includes determining that the indoor temperature is dropped to a target room temperature. After the indoor temperature reaches this target room temperature, step 230 includes stopping the compressor to stop the flow of refrigerant and generally shut down the refrigeration loop.

Notably, conventional air conditioner units stop the indoor fan simultaneously with the stopping of the compressor. However, as described briefly above, surfaces within indoor portion often have a temperature below the dew point temperature of the air within the room after a cooling cycle. Therefore, to prevent condensation from forming on these surfaces, method 200 includes, at step 240, operating the indoor fan after stopping the compressor. The indoor fan may continue to run and circulate the relatively warm room air through the relatively cool indoor heat exchanger and over the relatively cool surfaces until their temperature is raised sufficiently above the dew point temperature to prevent excessive condensation.

According to an exemplary embodiment, step 250 includes stopping the indoor fan when a fan stop condition occurs. As used herein, “fan stop condition” is generally used to describe any system condition, operating parameter, or other indication that the indoor fan may be stopped with minimal risk of condensation forming on components within the indoor portion. Although several exemplary fan stop conditions will be described below, it should be appreciated that controller 64 may be configured for detecting any other suitable operating parameters or conditions and regulating the operation of indoor fan and/or other components of unit 10 to reduce the likelihood of condensation in response to such conditions.

According to an exemplary embodiment, the fan stop condition occurs when a predetermined amount of time has passed after the compressor is stopped. For example, the predetermined amount of time may be determined empirically by the controller or may be programmed by the manufacturer of the unit. In this regard, for example, the manufacturer may estimate the amount of time that an indoor fan must run to warm the surfaces within the indoor portion sufficiently to prevent condensation performing. This estimate may be based on standard operating conditions experienced by the unit, historical cycle data, and/or real-time data provided by one or more system or remote sensors.

According to another embodiment, the fan stop condition occurs when the measured discharge temperature exceeds a bulk dew point temperature of the air within the room. In this regard, controller 64 may be configured for obtaining a dew point temperature using the humidity sensor using calculations known in the art. In addition, the controller can obtain the discharge temperature from the temperature sensor and trigger the fan stop condition when the discharge temperature exceeds the dew point temperature. Notably, stopping indoor fan after the discharge temperature exceeds the dew point temperature may prevent some or all condensation from forming on components within indoor portion of the unit with minimal lost energy, e.g. due to prolonged operation of indoor fan after compressor is shut off.

According to still another embodiment, the fan stop condition may occur when the discharge temperature exceeds any other suitable target temperature. For example, the indoor fan may be shut off when the discharge temperature has exceeded an elevated target temperature, i.e., a target temperature that is elevated relative to the dew point temperature. In this manner, the likelihood of condensation forming is reduced even further. For example, the elevated target temperature may be greater than the dew point temperature by at least 2° F., or by an even greater margin. Although an exemplary elevated target temperature is described herein, it should be appreciated that any fan stop temperature may be set by the manufacturer, determined by the user, or determined in any other suitable manner for minimizing the likelihood that condensation will form after the indoor fan has stopped operating.

FIG. 9 depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that the steps of any of the methods discussed herein can be adapted, rearranged, expanded, omitted, or modified in various ways without deviating from the scope of the present disclosure. Moreover, although aspects of method 200 are explained using unit 10 as an example, it should be appreciated that this method may be applied to operate any suitable air conditioner unit.

Referring now to FIG. 10, a plot is provided which illustrates the discharge temperature relative to the dew point temperature as the indoor fan operates after the compressor is turned off according to an exemplary embodiment. In this regard, the dew point temperature (as indicated by line 150) stays relatively constant while the sealed system remains off. Although the dew point temperature is illustrated as remaining perfectly constant, it should be appreciated that in reality the dew point temperature may vary with time. The measured discharge temperature (as indicated by line 152) generally increases as the indoor fan continues to run after the compressor is turned off.

More specifically, according to the illustrated embodiment, when the indoor temperature drops below the target temperature, the compressor is turned off (i.e., as indicated at time T0). At this point, the measured discharge temperature is much lower than the dew point temperature such that condensation would likely form in indoor components if the indoor fan is turned off simultaneously. Therefore, according to exemplary embodiments, the indoor fan continues to run after T0, thereby increasing the measured discharge temperature. At time T1 the measured discharge temperature is equal to the dew point temperature. According to an exemplary embodiment, the indoor fan may be shut off at T1 and the likelihood of condensation forming would be reduced. According still another embodiment, the indoor fan may continue to run until the measured discharge temperature reaches an elevated target temperature (i.e., relative to the dew point temperature) as indicated by line 154. According to the illustrated embodiment, this occurs at time T2. By shutting off the indoor fan at time T2, the likelihood of condensation may be reduced even more than if the indoor fan is stopped at T1.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A packaged terminal air conditioner unit comprising: a bulkhead defining an indoor portion and an outdoor portion; a refrigeration loop comprising an outdoor heat exchanger positioned within the outdoor portion and an indoor heat exchanger positioned within the indoor portion; a compressor operably coupled to the refrigeration loop and being configured for urging a flow of refrigerant through the outdoor heat exchanger and the indoor heat exchanger; an indoor fan configured for urging a flow of discharge air through the indoor heat exchanger and out a discharge vent; and a controller operably coupled to the compressor and the indoor fan, the controller being configured for: operating the compressor and the indoor fan to lower an indoor temperature; determining that the indoor temperature has dropped to a target room temperature; stopping the compressor in response to determining that the indoor temperature has dropped to the target room temperature; operating the indoor fan after stopping the compressor; and stopping the indoor fan when a fan stop condition occurs.
 2. The packaged terminal air conditioner unit of claim 1, wherein the fan stop condition occurs when a predetermined amount of time has passed since stopping the compressor.
 3. The packaged terminal air conditioner unit of claim 2, wherein the predetermined amount of time is empirically determined by the controller.
 4. The packaged terminal air conditioner unit of claim 1, wherein the packaged terminal air conditioner unit further comprises: a discharge temperature sensor positioned within the indoor portion for measuring a discharge temperature; and a humidity sensor positioned within the indoor portion for measuring an indoor humidity.
 5. The packaged terminal air conditioner unit of claim 4, wherein the controller is further configured for: obtaining a dew point temperature using the humidity sensor; obtaining the discharge temperature using the discharge temperature sensor; and determining that the fan stop condition occurs when the discharge temperature exceeds the dew point temperature.
 6. The packaged terminal air conditioner unit of claim 4, wherein the controller is further configured for: obtaining a dew point temperature using the humidity sensor; determining an elevated target temperature based on the dew point temperature; and determining that the fan stop condition occurs when the discharge temperature has exceeded the elevated target temperature.
 7. The packaged terminal air conditioner unit of claim 6, wherein the elevated target temperature is greater than the dew point temperature by at least 2 degrees Fahrenheit.
 8. The packaged terminal air conditioner unit of claim 4, wherein the humidity sensor is positioned within the indoor portion upstream of the indoor fan.
 9. The packaged terminal air conditioner unit of claim 4, wherein the discharge temperature sensor is positioned within the indoor portion proximate the discharge vent.
 10. The packaged terminal air conditioner unit of claim 1, further comprising an indoor temperature sensor for measuring the indoor temperature.
 11. A method of operating a packaged terminal air conditioner unit, the packaged terminal air conditioner unit comprising a compressor and an indoor fan, the method comprising: operating the compressor and the indoor fan to lower an indoor temperature; determining that the indoor temperature has dropped to a target room temperature; stopping the compressor in response to determining that the indoor temperature has dropped to the target room temperature; operating the indoor fan after stopping the compressor; and stopping the indoor fan when a fan stop condition occurs.
 12. The method of claim 11, wherein the fan stop condition occurs when a predetermined amount of time has passed since stopping the compressor.
 13. The method of claim 12, wherein the predetermined amount of time is empirically determined.
 14. The method of claim 11, further comprising: obtaining a dew point temperature using a humidity sensor; obtaining a discharge temperature using a discharge temperature sensor; and determining that the fan stop condition occurs when the discharge temperature exceeds the dew point temperature.
 15. The method of claim 11, further comprising: obtaining a dew point temperature using the humidity sensor; obtaining a discharge temperature using a discharge temperature sensor; determining an elevated target temperature based on the dew point temperature; and determining that the fan stop condition occurs when the discharge temperature has exceeded the elevated target temperature.
 16. The method of claim 15, wherein the elevated target temperature is greater than the dew point temperature by at least 2 degrees Fahrenheit.
 17. An air conditioner unit comprising: a compressor configured for urging a flow of refrigerant through an outdoor heat exchanger and an indoor heat exchanger; an indoor fan configured for urging a flow of discharge air through the indoor heat exchanger and out a discharge vent; a discharge temperature sensor; a humidity sensor; and a controller operably coupled to the compressor and the indoor fan, the controller being configured for: operating the compressor and the indoor fan to lower an indoor temperature; stopping the compressor when the indoor temperature drops below a target temperature; obtaining a dew point temperature using the humidity sensor; determining a fan stop temperature based on the dew point temperature; obtaining a discharge temperature using the discharge temperature sensor; and stopping the indoor fan when the discharge temperature exceeds the fan stop temperature.
 18. The air conditioner unit of claim 17, wherein the fan stop temperature is higher than the dew point temperature.
 19. The air conditioner unit of claim 17, wherein the humidity sensor is positioned upstream of the indoor fan.
 20. The air conditioner unit of claim 17, wherein the discharge temperature sensor is positioned proximate the discharge vent. 